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Running the foil is slang for the act of smoking heroin off of aluminum foil. Opioid users typically use a flame to heat heroin or fentanyl on a piece of foil while inhaling the vapors, also known as chasing the dragon. Running foil is extremely potent and hard on the lungs, and is considered a step below shooting up. The term originates from the way in which melted heroin runs on foil as its vaporized, often leaving a trail of residue. It is also common for opioid addicts to smoke percocet M30 pills off foil.
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